Question

which substance is an element?
a carbon
b air
c fire
d water

Explanation:

• Carbon: An element, represented by the symbol \(C\) on the periodic table. It consists of only one type of atom.
• Air: A mixture of gases like nitrogen (\(N_2\)), oxygen (\(O_2\)), carbon - dioxide (\(CO_2\)) etc.
• Fire: A chemical reaction (exothermic oxidation) and not a substance in the sense of being an element, compound or mixture.
• Water: A compound with the chemical formula \(H_2O\), made up of hydrogen (\(H\)) and oxygen (\(O\)) atoms.

Answer:

A. carbon